Traditional annotation and white boarding systems have been designed for a single-user presentation case where the presenting user stands at the front of the room and interacts with the display directly to mark-up and draw on the display itself. Other annotation systems allow a user, using a digital pen or even the user's fingers on a touch display, to touch and draw on the digital display surface over the top of existing content. The user's touch points directly denote the point on the display where a corresponding drawing event should occur. For example, when a user touches point (x,y)1 and drags her/his finger to point (x,y)2 the annotation system may draw a line between those two pixel locations on the display. This technique has been extended to support multiple users who are interacting with the display simultaneously.
Alternatives to this model have been introduced by allowing users to interact with a simulated display on their own device. Users can then remain in place to draw on a local display and then those annotations are translated to the display in the room for group viewing.